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Rear Defrost Not Working - Tricks?

20K views 43 replies 20 participants last post by  Petrolhead99 
#1 ·
So I'm one month into a new to me 2018 Giulia Sport. We got some snow this morning and I was attempting to run my rear defrost after clearing the windows, but it is obviously not working. Front defrost works too good. Anyone else encounter this issue? Is there an easy trick/fix without carting it all of the way to the dealership?
 
#2 ·
It's a known problem with the battery charge...... If the charge is below a certain level, the car starts to disable certain options, the rear windscreen defrost being one of them.....
Driving may help, using a trickle charger definately helps.....
 
#3 ·
I assume the light turns on when you hit the button? Check the base of rear window for a connector to make sure it is hooked up to the window. If it is, it could be that someone damaged the physical lines on the window, but that typically just renders one section not working instead of the whole window.
@jwq2 is probably the correct answer.
 
#9 ·
Remember, after charging the battery it may take a couple of overnight cycles for the IBS(battery sensor) to register your battery state of charge with the body control module. The vehicle may have to sit over five hours, two or three times after driving, for the vehicle to properly register a good battery.
 
#10 ·
When I first got the car same thing happened. Took it back to the dealer I purchased it from and they charged the battery back up and start/stop defrost worked for 3 days then it stopped.
I took the car to a closer dealer that i'll be using for all my work. They tested the battery, it was good. The problem was the IBS or battery sensor. That was replaced and I am going on day 7 with no issues... I'll keep you posted. I do not trickle charge my battery however I drive about 25 miles on the highway every other day.
 
#15 · (Edited)
The problem is the software algorithms used to control the charging by the alternator, that have a bias towards economy in stead of max battery charge.....
Maximum charging current occurs f.i. at low speeds and during braking..... There is not much to be done about this, other then Alfa improving the software (and for now helping things along with trickle charging etc.)
I did read that it appears things have been improved in the latest (2021?) models, so hopefully there will be software updates coming.....
 
#18 ·
How does the front defrost (defog?) work "too good"?
 
#20 ·
#27 · (Edited)
Take it to the dealership and let them correct it. You've only had it for a month. I have a 2018 ti Lusso with 35,000 miles on it. It's on the original Varta battery and I never use a trickle charger. I drive 1.5 miles to and from home to work and back plus local errands as well most days. Occasional longer trips but not routine. Had an issue with the battery discharge issue 2 years ago and my dealer did some software updates including the IBS and as above, trouble free ever since. I did start keeping my key fobs stored in faraday pouches since at home the car is rarely more than 20 - 25 feet away from where my keys are stored. If you have a similar situation I suggest you try that as well since otherwise the fobs and the car will be in constant communication with each other.
 
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